Flexible self-expandable stent using a shape memory alloy and method and apparatus for fabricating the same

ABSTRACT

Disclosed herein is a flexible self-expandable stent using shape memory alloy for expanding stenosal portions and method and apparatus for fabricating the same. The self-expandable stent using shape memory allow, comprises a first cylindrical stent member comprised of a first wire formed of super elastic shape memory alloy, the first wire being bent a large number of times while being extended upwardly and downwardly a large number of times, so the first wire forms a plurality of variable rhombic spaces by forming a plurality of intersections for causing the first wire to be intersected with itself to resist longitudinal constriction of the first cylindrical stent member and a plurality of interlocked points for causing the first wire to be interlocked with itself at spaced positions to allow longitudinal constriction of the first cylindrical stent member; and a second cylindrical stent member comprised of a second wire formed of super elastic shape memory alloy, the second wire being diagonally extended in parallel with the previously positioned first wire and passed alternately under and over the first wire so as to divide each of a plurality of rhombic spaces formed in the first cylindrical stent member into four equal parts, thereby preventing the first and second cylindrical stent members from being separated from each other.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to a flexible self-expandablestent using shape memory alloy for expanding stenosal portions andmethod and apparatus for fabricating the same, and more particularly toa flexible self-expandable stent using shape memory alloy and method andapparatus for fabricating the same, used to be situated in and expandthe passages of stenosal portions so as to deal with the stenosis of ablood vessel caused by thrombus and the stenosis of the gullet, the gallduct and the urethra caused by cancer tissues and the formation of theartificial passage in the jugular vein, which is capable of beingpositioned to fit the shape of the passage of the stenosal portionregardless of the shape of the passage, such as a straight (horizontalor vertical) passage and a winding passage, while maintaining itstransversal elasticity, thereby maintaining the shape of the passage andminimizing the deformation of the stenosal portion.

2. Description of the Prior Art

In general, a blood vessel is blocked or constricted because ofthrombus, arteriosclerosis or the like, so a variety of disorders occur.

When a blood vessel is being constricted or has been constricted, thestenosal portion of the blood vessel is treated through artificialvessel replacement or angioplasty by means of a surgical operation.

However, such a surgical operation requires the incision of the largebody region around a pathological portion, so a large scar remains, along period of convalescence is required and the insufficient effect ofan operation is achieved.

In particular, most vascular diseases are caused by hypertension and aheart disease, so it is impossible to treat most vascular disease bymeans of the surgical operation.

In order to overcome such a problem, there is employed angioplastywithout an surgical operation, in which a small hole is bored into afemoral artery, a balloon catheter tube is inserted into a stenosalportion through the small hole from the outside of the body into theinside of a blood vessel, and the balloon of the balloon catheter tubeis inflated.

However, in accordance with angioplasty, a blood vessel isre-constricted three or four months after an operation. Accordingly,angioplasty should be carried out again, so there occurs a problem thata patient should undergo pain and economic difficulty.

Excepting such vascular diseases, when the gullet is blocked by cancertissues, it is impossible to take food through the mouth. Accordingly, ahole is formed from the abdomen to the stomach and foot is supplied tothe stomach through a tube, so pain is caused to a patient and hiscaregivers.

The stenosis of the gall duct and the urethra, the formation of theartificial passage in the jugular vein and the stenosis and blockade ofthe internal organs are dealt with in such a way.

In such cases, there occurs a problem that mental or economic burden isimposed on a patient and his caregivers.

In order to solve the problems of the prior art, the present inventorsfiled an expandable stent using shape memory alloy and method forfabricating the expandable stent (Korean Pat. Appln. No. 98-13572). Thisapplication, as can be seen in FIGS. 1 to 4, discloses a prior artexpandable stent in which a super-elastic shape memory alloy wire 1 isintersected with itself and woven to form a plurality of rhombic spaces2 and a hollow cylindrical body 3 having a certain length, a pluralityof entrance and exit bends are formed at both ends of the hollowcylindrical body 3, and both ends 6 and 7 of the super-elastic shapememory alloy wire 1 are welded together. In the placement of theexpandable stent, the hollow cylindrical body 3 is considerably reducedin volume by compressing the rhombic spaces 2 and the prior artexpandable stent 8 is pushed into a pathological portion B-1 within avessel B using a guide catheter G.T and a pusher catheter P.C, therebyexpanding the vessel B by pushing the pathological portion B-1 radiallyoutwardly. Accordingly, the prior art expandable stent 8 can besemi-permanently utilized to expand the stenosal portion of the body.

The use of the prior art technology of the present inventors isdescribed with reference to FIG. 3. The position, length and innerdiameter of the pathological portion B-1 situated within the vessel Bare examined by means of a fluoroscope used in angioplasty, and therequired portion is firstly anesthetized.

In this state, the guide tube G.T is inserted into the vessel B to reachthe pathological portion B-1, and the prior art expandable stent 8 isinserted into the guide tube G.T while being constricted in width(diameter). In this state, the prior art expandable stent 8 is pushedinto the pathological portion B-1 using a pusher catheter P.C.

The expandable stent 8 positioned in the pathological portion B-1 isrestored to its original shape while being removed from the guide tubeG.T, and simultaneously pushes the pathological portion situated in thevessel B to expand the vessel B, thereby expanding the passage of thevessel B of the stenosal portion.

In this case, the prior art expandable stent 8, as shown in FIG. 1, hasthe diameter Ø 10 to 30% larger than that of an applied portion, thatis, a portion of a blood vessel B, and the length L longer than that ofan applied portion, that is, a portion of a blood vessel B.

In accordance with the previously filed prior art of the presentinventors, the expandable stent using super-elastic shape memory alloywire 1 and having a diameter Ø and a length L has radial andlongitudinal elasticity tending to be restored to its original stateunless the shape memory alloy wire 1 is forcibly compressed by externalforce.

However, the expandable stent 8 in accordance with the prior art can beapplied to the straight line-shaped vessel B without hindrance, but isnot applicable to a winding stenosal vessel B shown in FIG. 4, therebydecreasing the usability of the expandable stent 8.

The reason for this is that when the prior art expandable stent 8 isinserted into the winding stenosal vessel B, the prior art expandablestent 8 does not maintain the shape corresponding to that of the windingvessel B but is restored to its straight line (horizontal or vertical)shape. Accordingly, the vessel B is lengthened and the winding portionof the vessel B is straightened (horizontally or vertically, so theentrance of the vessel B is deformed to be narrower than its originalsize (t→t-a), thereby hindering the circulation of material anddeteriorating the function of the expandable stent.

SUMMARY OF THE INVENTION

Accordingly, the present invention has been made keeping in mind theabove problems occurring in the prior art, and an object of the presentinvention is to provide a self-expandable stent used to be situated inand expand the passage of a stenosal portion, which is capable of beingpositioned to fit the shape of the passage of the stenosal portionregardless of the shape of the passage, such as a straight (horizontalor vertical) passage and a winding passage, while maintaining itstransversal elasticity, thereby maintaining the original shape of thepassage and minimizing the deformation of the stenosal portion.

In order to accomplish the above object, the present invention providesa self-expandable stent using shape memory allow, comprising: a firstcylindrical stent member comprised of a first wire formed of superelastic shape memory alloy, the first wire being bent a large number oftimes while being extended upwardly and downwardly a large number oftimes, so the first wire forms a plurality of variable rhombic spaces byforming a plurality of intersections for causing the first wire to beintersected with itself to resist longitudinal constriction of the firstcylindrical stent member and a plurality of interlocked points forcausing the first wire to be interlocked with itself at spaced positionsto allow longitudinal constriction of the first cylindrical stentmember; and a second cylindrical stent member comprised of a second wireformed of super elastic shape memory alloy, the second wire beingdiagonally extended in parallel with the previously positioned firstwire and passed alternately under and over the first wire so as todivide each of a plurality of rhombic spaces formed in the firstcylindrical stent member into four equal parts, thereby preventing thefirst and second cylindrical stent members from being separated fromeach other.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and other advantages of thepresent invention will be more clearly understood from the followingdetailed description taken in conjunction with the accompanyingdrawings, in which:

FIG. 1 is a front view of a prior art expandable stent;

FIG. 2 is a side sectional view of FIG. 1;

FIG. 3 is a view showing the operation of the prior art expandable stentof FIG. 1;

FIG. 4 is a view showing the application of the prior art expandablestent of FIG. 1 to a blood vessel;

FIGS. 5 and 6 are a perspective view and a sectional view showing thebase jig of the present invention, respectively;

FIGS. 7 a, 7 b, 7 c and 7 d are development views showing thefabrication method of the present invention;

FIG. 8 is a development view showing a completed self-expandable stent;

FIG. 9 is a front view showing the self-expandable stent of the presentinvention;

FIGS. 10 and 11 are detailed views showing the principal portions of theself-expandable stent of the present invention; and

FIGS. 12 and 13 are views showing the application of the self-expandablestent of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, the present invention is described in detail with referenceto FIGS. 5 to 13.

The material of a wire employed in the present invention is the same asthat of the invention of a patent application previously filed by theinventors of the present invention.

The material employed in the present invention is shape memory alloythat can be formed in the shape of a hollow cylinder and heat-treated tobe restored to its original shape at a predetermined temperature.

There are utilized various kinds of shape memory alloy. Ni—Ti linealloy, which has super-elasticity after heat treatment and superiorshape memory characteristics, is most suitable for the embodying of thepresent invention.

The self-expandable stent of the present invention is fabricated usingtwo super-elastic shape memory alloy wires each having a diameterranging from 0.1 to 0.5 mm. A first cylindrical stent member X iscomprised of a first wire 10 formed of super-elastic shape memory alloy.The first wire 10 is bent a large number of times while being extendedupwardly and downwardly a large number of times, so the first wire 10forms a plurality of variable rhombic spaces 20 by forming a pluralityof intersections 70 for causing the first wire 10 to be intersected withitself to resist the longitudinal constriction of the first cylindricalstent member X and a plurality of interlocked points 60 for causing thefirst wire 10 to be interlocked with itself at spaced positions to allowthe longitudinal constriction of the first cylindrical stent member X. Asecond cylindrical stent member Y is comprised of a second wire 11. Thesecond wire 11 is diagonally extended in parallel with the previouslypositioned first wire 10 and passed alternately under and over the firstwire 10 so as to divide each of a plurality of rhombic spaces formed inthe first cylindrical stent member X into four equal parts. Theself-expandable stent 80 of the present invention is completed byjoining together the first and second cylindrical stent member members Xand Y.

FIGS. 5 and 6 are views illustrating a stent fabricating apparatus. Acylinder 110 having a desired diameter Ø and a desirable length L isutilized to fabricate the self-expandable stent 80 of the presentinvention. In this case, a plurality of circumference dividing lines a0,a1, a2, a3, - - - , a9 and a plurality of length dividing lines b0, b1,b2, b3, - - - , b7 are set by regularly dividing the circumference W andlength L of the cylinder 110, respectively.

A plurality of assembly grooves 130 are formed along the length of thecylinder 110 with reference to the circumference dividing lines a0, a1,a2, a3, - - - , a9. A plurality of projected pins 120 are detachablyimplanted at all the intersections between the circumference dividinglines a0, a1, a2, a3, - - - , a9 and the length dividing lines b0, b1,b2, b3, - - - , b7 at their one-side ends. A plurality of assemblyauxiliary grooves 130′ are each formed between two neighboring assemblygrooves 130.

The above-described setting is for the understanding of the presentinvention.

In other words, although the present invention is described using thecircumference dividing lines a0, a1, a2, a3, - - - , a9 and the lengthdividing lines b0, b1, b2, b3, - - - , b7 set by regularly dividing thecircumference W and length L of the cylinder 110 of the base jig 100,this is for easy understanding of the present invention. Accordingly,the circumference dividing lines and the length dividing lines can beoptionally set according to the size of the stent 80, that is, thediameter and length of the stent 80.

In other words, a plurality of assembly grooves 130 are formed withreference to a relatively large or small number of circumferencedividing lines a0, a1, a2, a3, - - - , a9, - - - and a relatively largeor small number of length dividing lines b0, b1, b2, b3, - - - ,b7, - - - can be set as described beforehand, thus fabricating theself-expandable stent 80 of the present invention.

A fixing pin 99 is implanted at the uppermost position of the base jig100.

FIGS. 7 a to 7 d are development views showing a developed base jig 100so as to describe the fabrication method of the present invention.

The procedure for fabricating the first cylindrical stent member X isdescribed with reference to FIGS. 7 a and 7 b.

As shown in FIG. 7 a, a knot 98 is formed by tying a first wire 10 atits one end. The knot 98 is inserted into the pin 99 to secure the wire10.

The knot 98 is selected as a start point S for convenience.

One of the circumference dividing lines a0, a1, a2, a3, - - - , a9 isselected as a first reference line a0. The first wire 10 is diagonallyextended while being diagonally downwardly passed by a projected pin 120(its position: a0b0) situated at the uppermost position of the firstreference line a0, and hooked around a projected pin 120 (its position:a1b1) by passing the first wire 10 under the projected pin 120 (itsposition: a1b1).

In such a case, the length by which the first wire 10 has beendiagonally extended is referred to as a diagonal length for convenience.

After the first wire 10 is hooked around the projected pin 120 (itsposition: a1b1) by passing the first wire 10 under the projected pin 120(its position: a1b1) and diagonally upwardly extending it, the firstwire 10 undergoes the process in which the first wire 10 is hookedaround a projected pin 120 (its position: a2b0) by passing the firstwire 10 over the projected pin 120 (its position: a2b0) and diagonallydownwardly extending the first wire 10.

Thereafter, the first wire 10 is extended to a projected pin 120 (itsposition: a4b2) by the diagonal distance of 2, and passed under theprojected pin 120 (its position: a4b2) and extended diagonally upwardly.

Thereafter, the first wire 10 is extended to a projected pin 120 (itsposition: a5b1) by the diagonal distance of, and passed over theprojected pin 120 (its position: a5b1) and extended diagonallydownwardly. Thereafter, the first wire 10 is extended to a projected pin120 (its position: a6b2) by the diagonal distance of , and passed underthe projected pin 120 (its position: a6b2) and extended diagonallyupwardly.

In such a state, after the first wire 10 is hooked around a projectedpin 120 (its position: a7b1) by diagonally upwardly extending the firstwire 10 by the diagonal distance of and passing it over the projectedpin 120 (its position: a7b3), the first wire 10 is hooked around aprojected pin 120 (its position: a9b3) by diagonally downwardlyextending the first wire 10 by the diagonal distance of 2 and passing itunder the projected pin 120 (its position: a9b3).

After such a process, the first wire 10 is hooked around a projected pin120 (its position: a0b2) by passing the first wire 10 over the projectedpin 120 (its position: a0b2), and, thereafter, is hooked around aprojected pin 120 (its position: a1b3) by passing the first wire 10under the projected pin 120 (its position: a1b3).

As described above, after the first wire 10 has been hooked around theprojected pin 120 (its position: a1b3) while diagonally downwardlypassing the first wire 10 under the projected pin 120 (its position:a1b3), the first wire 10 is hooked around a projected pin 120 (itsposition: a2b2) by diagonally upwardly extending the first wire 10 andpassing it over the projected pin 120 (its position: a2b2). Thereafter,the first wire 10 is extended to a projected pin 120 (its position:a4b4) by the diagonal distance of 2, and hooked around the projected pin120 (its position: a4b4) by passing the first wire 10 under theprojected pin 120 (its position: a4b4).

After such a process is completed, the first wire 10 is diagonallyupwardly extended to a projected pin 120 (its position: a5b3) by thediagonal distance of , and hooked around the projected pin 120 (itsposition: a5b3) by passing the first wire 10 over the projected pin 120(its position: a5b3).

Next, the first wire 10 is hooked around a projected pin 120 (itsposition: a6b4) by diagonally upwardly extending the first wire 10 undera projected pin 120 (its position: a6b4) by the diagonal distance of andpassing it over the projected pin 120 (its position: a6b4).

In such a state, after the first wire 10 is hooked around a projectedpin 120 (its position: a7b3) by diagonally upwardly extending the firstwire 10 by the diagonal distance of and passing it over the projectedpin 120 (its position: a7b3), the first wire 10 is hooked around aprojected pin 120 (its position: a9b5) by diagonally downwardlyextending the first wire 10 by the diagonal distance of 2 and passing itunder the projected pin 120 (its position: a9b5).

After such a process, the first wire 10 is hooked around a projected pin120 (its position: a0b4) by passing the first wire 10 over the projectedpin 120 (its position: a0b4), and, thereafter, is hooked around aprojected pin 120 (its position: a1b5) by passing the first wire 10under the projected pin 120 (its position: a1b5).

As described above, since the first wire 10 has been hooked around theprojected pin 120 (its position: a1b5) while passing the first wire 10under the projected pin 120 (its position: a1b5), the first wire 10should be hooked around a projected pin 120 (its position: a2b4) bydiagonally upwardly extending the first wire 10 and passing it over theprojected pin 120 (its position: a2b4). Thereafter, the first wire 10 isextended to a projected pin 120 (its position: a2b4) by the diagonaldistance of 2, and hooked around the projected pin 120 (its position:a4b6) by passing the first wire 10 under the projected pin 120 (itsposition: a4b6).

After such a process is completed, the first wire 10 is diagonallyupwardly extended to a projected pin 120 (its position: a5b5) by thediagonal distance of , and hooked around the projected pin 120 (itsposition: a5b5) by passing the first wire 10 over the projected pin 120(its position: a5b5).

Next, the first wire 10 is hooked around a projected pin 120 (itsposition: a6b6) by diagonally upwardly extending the first wire 10 undera projected pin 120 (its position: a6b6) by the diagonal distance of andpassing it over the projected pin 120 (its position: a6b6).

In such a state, after the first wire 10 is hooked around a projectedpin 120 (its position: a7b5) by diagonally upwardly extending the firstwire 10 by the diagonal distance of and passing it over the projectedpin 120 (its position: a7b5), the first wire 10 is hooked around aprojected pin 120 (its position: a9b7) by diagonally downwardlyextending the first wire 10 by the diagonal distance of 2 and passing itunder the projected pin 120 (its position: a9b7).

In such a state, after the first wire 10 is hooked around a projectedpin 120 (its position: a0b6) by diagonally upwardly extending the firstwire 10 by the diagonal distance of and passing it over the projectedpin 120 (its position: a0b6), the first wire 10 is hooked around aprojected pin 120 (its position: a1b7), a projected pin 120 (itsposition: a2b7), a projected pin 120 (its position: a3b7) and aprojected pin 120 (its position: a4b6).

In this case, the projected pin 120 (its position: a4b6) is used forallowing the first wire 10 to be twice hooked around itself. As shown inthe enlarged view of FIG. 7 a, the later hooked first wire 10 is hookedaround the projected pin 120 in such a way that the later hooked firstwire 10 is passed under the previously hooked first wire 10, hookedaround the projected pin 120 (its position: a4b6), and passed over thepreviously hooked first wire 10.

This process can be performed using the assembly auxiliary grooves 130′formed on the base jig 100.

In such a state, the first wire 10 reaches a projected pin 120 (itsposition: a5b7) and a projected pin 120 (its position: a6b6). In thiscase, the first wire 10 is twice hooked around the projected pin 120(its position: a6b6) in the same way as that for the projected pin 120(its position: a4b6).

In such a state, the first wire 10 reaches a projected pin 120 (itsposition: a7b7) and a projected pin 120 (its position: a8b6). In thiscase, the first wire 10 is twice hooked around the projected pin 120(its position: a8b6) in the same way as that for the projected pin 120(its position: a4b6).

Thereafter, after the first wire 10 is hooked around a projected pin 120(its position: a9b7), the first wire 10 is diagonally upwardly extendedby the distance of 2 and hooked around a projected pin 120 (itsposition: a1b5).

Such a process is indicated as the arrow “d” of FIG. 7 a and the arrow“d” of FIG. 7 b associated with each other. The arrows “a”, “b” and “c”of FIG. 7 a are marks for indicating the extending paths of the firstwire 10 so as to allow the present invention to be easily understood.

The dotted lines of FIG. 7 b indicate the first wire 10 that hasundergone the above-described procedure, while the solid lines of FIG. 7b indicate the first wire 10 that will undergo the below-describedprocedure.

After the first wire 10 is hooked around the projected pin 120 (itsposition: a1b5) by diagonally downwardly extending the first wire 10from the projected pin 120 (its position: a1b5) by the diagonal distanceof and passing the first wire 10 under the projected pin 120 (itsposition: a2b6), the first wire 10 is hooked around the projected pin120 (its position: a4b4) by diagonally upwardly extending the first wire10 by the diagonal distance of 2 and passing the first wire 10 over theprojected pin 120 (its position: a4b4). Thereafter, the first wire 10 ishooked around the projected pin 120 (its position: a6b4) by diagonallyupwardly extending the first wire 10 by the diagonal distance of andpassing the first wire 10 over the projected pin 120 (its position:a6b4).

After the first wire 10 is hooked around the projected pin 120 (itsposition: a7b5) by diagonally downwardly extending the first wire 10 bythe diagonal distance of and passing the first wire 10 under theprojected pin 120 (its position: a7b5), the first wire 10 is hookedaround the projected pin 120 (its position: a9b3) by diagonally upwardlyextending the first wire 10 by the diagonal distance of 2 and passingthe first wire 10 over the projected pin 120 (its position: a9b3).Thereafter, the first wire 10 is hooked around the projected pin 120(its position: a0b4) by diagonally upwardly extending the first wire 10by the diagonal distance of and passing the first wire 10 over theprojected pin 120 (its position: a5b3) (refer to arrow “e”).

After the first wire 10 is hooked around the projected pin 120 (itsposition: a6b2) by diagonally upwardly extending the first wire 10 bythe diagonal distance of and passing the first wire 10 over theprojected pin 120 (its position: a6b2), the first wire 10 is hookedaround the projected pin 120 (its position: a7b3) by diagonallydownwardly extending the first wire 10 by the diagonal distance of andpassing the first wire 10 under the projected pin 120 (its position:a7b3).

After the first wire 10 is hooked around the projected pin 120 (itsposition: a9b1) by diagonally upwardly extending the first wire 10 bythe diagonal distance of 2 and passing the first wire 10 over theprojected pin 120 (its position: a6b2), the first wire 10 is hookedaround the projected pin 120 (its position: a0b2) by diagonallydownwardly extending the first wire 10 by the diagonal distance of andpassing the first wire 10 under the projected pin 120 (its position:a0b2) (refer to arrow “f”).

After the first wire 10 is hooked around the projected pin 120 (itsposition: a1b1) by diagonally upwardly extending the first wire 10 bythe diagonal distance of and passing the first wire 10 under theprojected pin 120 (its position: a1b1), the first wire 10 is hookedaround the projected pin 120 (its position: a2b2) by diagonallydownwardly extending the first wire 10 by the diagonal distance of andpassing the first wire 10 over the projected pin 120 (its position:a2b2). Thereafter, the first wire 10 is hooked around the projected pin120 (its position: a4b0) by diagonally upwardly extending the first wire10 by the diagonal distance of 2 and passing the first wire 10 under theprojected pin 120 (its position: a4b0).

The first wire 10 is hooked on the projected pins (their positions:a6b0, a7b1, a8b0 and a9b1) by diagonally and downwardly extending thefirst wire 10 by the diagonal length of and alternately passing thefirst wire 10 by the projected pins (their positions: a6b0, a7b1, a8b0and a9b1).

After the first wire 10 is hooked on the projected pin 120 (itsposition: a9b1), the first wire 10 reaches the initial projected pin(its position: a9b1). There is fabricated the first cylindrical stentmember X in which its both ends are connected to each other by weldingtogether both ends of the first wire 10 meeting each other, or insertingboth ends of the first wire 10 into a sleeve 200 and pressing them.

As described above, in fabricating the first cylindrical stent member X,the first cylindrical stent member X is fabricated in the process ofextending the first wire 10 from the top of the jig 100 to the bottom ofthe jig 100 and from the bottom of the jig 100 to the top of the jig100.

In such a case, when the first wire 10 is desired to be hooked aroundthe same projected pin 120 as that around which the first wire 10 hasbeen hooked, the first wire 10 should be passed under or over thepreviously placed first wire 10 so that the first wire 10 is situated athigh and low positions.

After the first cylindrical stent member X is fabricated, the secondcylindrical stent member Y is fabricated. The fabrication of the secondcylindrical stent member Y is illustrated in FIGS. 7 c and 7 d.

The second cylindrical stent member Y is fabricated while being passedby the projected pins 120 that are not utilized in fabricating the firstcylindrical stent member X.

A knot 98 is formed by tying a second wire 11 at its one end. The knot98 is inserted into a fixing pin 99 to secure the wire 10, which isindicated as a start point S.

In such a state, the second wire 11 is diagonally extended in parallelwith the first wire 10 while being hooked around the projected pin (itsposition: a1b0), and is hooked around the projected pin (its position:a8b7) by passing the second wire 11 under the projected pin (itsposition: a8b7) situated in the lowest position ((1) position).

In such a case, if the second wire 11 firstly meets the previouslypositioned first wire 10 and is passed under the first wire 10 whilebeing extended to the projected pin (its position: a8b7), the secondwire 11 has to be passed over the previously positioned first wire 10that is secondly met by the second wire 11. The second wire 11 isalternately passed under and over the first wire 10 in such a way.

The second wire 11 is hooked by passing the second wire 11 under theprojected pin (its position: a8b5), and, thereafter, the second wire 11is hooked around the uppermost projected pin 120 (its position: a0b5) byextending the second wire 11 to the uppermost projected pin 120 (itsposition: a5b0) and passing the second wire 11 under the uppermostprojected pin 120 (its position: a5b0) (although in FIG. 7 c the secondwire 11 seems to be hooked around the projected pin 120 (its position:a0b5), the second wire 11 is extended along arrow “g”) ((2) position).

In such a state, the second wire 11 is bent by extending the second wire11 under the projected pin 120 (its position: a2b7) ((3) position).

In this case, although in FIG. 7 c the second wire 11 seems to be hookedaround the projected pin 120 (its position: a0b5), the second wire 11 isactually extended along arrow “h” because FIG. 7 c is a developmentview.

In this state, the second wire 11 is bent by extending the second wire11 over the projected pin 120 (its position: a9b0) ((4) position).

In this state, the second wire 11 is bent by extending the second wire11 under the projected pin 120 (its position: a6b7) ((5) position).

In this case, although in FIG. 7 c the second wire 11 seems to be hookedaround the projected pin 120 (its position: a0b1), the second wire 11 isextended along arrow “i” of FIG. 7 c and arrow “i” of FIG. 7 d becauseFIG. 7 c is a development view.

In this state, the second wire 11 is bent by extending the second wire11 over the projected pin 120 (its position: a3b0) ((6) position).

In this case, although in FIG. 7 d the second wire 11 seems to be hookedaround the projected pin 120 (its position: a0b1), the second wire 11 isextended along arrow “j” because FIG. 7 d is a development view.

In this state, the second wire 11 is bent by extending the second wire11 over the projected pin 120 (its position: a0b7) ((7) position).

In this state (in FIG. 7 d the movement of the second wire 11 isillustrated by arrow “k”), the second wire 11 is bent by extending thesecond wire 11 over the projected pin 120 (its position: a7b0) ((8)position).

In this state, the second wire 11 is bent by extending the second wire11 under the projected pin 120 (its position: a4b7) ((9) position).

In this case, although in FIG. 7 d the second wire 11 seems to be hookedaround the projected pin 120 (its position: a0b3), the second wire 11 isextended along arrow “1” because FIG. 7 d is a development view.

In this state, the second wire 120 reaches the initial projected pin 120(its position: a1b0) ((10) position).

There is fabricated the second cylindrical stent member Y in which itsboth ends are connected to each other by welding together both ends ofthe second wire 10 meeting each other, or inserting both ends of thefirst wire 10 into a thin, sleeve 200 and pressing them.

In this case, although in FIG. 7 d the second wire 11 seems to be hookedaround the projected pin 120 (its position: a0b1), the second wire 11 isextended along arrow “m” because FIG. 7 d is a development view.

As described above, the second wire 11 is diagonally extended inparallel with the previously positioned first wire 10 and passedalternately under and over the first wire 10 so as to divide each of aplurality of rhombic spaces formed in the first cylindrical stent memberX into four equal parts, thus forming the second cylindrical stentmember Y. The second cylindrical stent member Y together with the firstcylindrical stent member X functions to prevent the first and secondcylindrical stent members X and Y from being separated from each other.

Additionally, the second cylindrical stent member Y utilizes theprojected pins 120 other than the projected pins 120 that have beenutilized by the first cylindrical stent member X.

As described above, the fabricating method of the present invention isperformed while following a series of steps.

The first wire 10 undergoes the first step of being passed through thestart point S, being bent by being extended by the diagonal length ofand being passed by a first projected pin 120, being bent by beingdiagonally downwardly extended by the diagonal length of and passedunder a second projected pin 120, being bent by being diagonallyupwardly extended by the diagonal length of and passed over a thirdprojected pin 120, and being bent by being diagonally downwardlyextended by the diagonal length of 2 and passed under a fourth projectedpin 120.

The first wire 10 undergoes the second step of being bent by beingdiagonally upwardly extended by the diagonal length of and being passedover a fifth projected pin 120, being bent by being diagonallydownwardly extended by the diagonal length of and being passed under asixth projected pin 120, being bent by being diagonally upwardlyextended by the diagonal length of and passed over a second projectedpin 120, being bent by being diagonally downwardly extended by thediagonal length of 2 and passed under a seventh projected pin 120, andbeing bent by being diagonally upwardly extended by the diagonal lengthof and passed over an eighth projected pin 120.

The first wire 10 undergoes the third step of being extended downwardlyand upwardly six times each by a diagonal length of .

The first wire 10 undergoes the fourth step of following the first step,the second step, the first step, the second step, the first step, thesecond step, the third step, the reversed first step, the reversedsecond step, the reversed first step, the reversed second step and thereversed first step, and, thereafter, being extended downwardly andupwardly four times each by a diagonal length of.

The second wire 11 undergoes the first step, the second step five times,the fifth step of being extended downwardly and upwardly each by adiagonal length of , the reversed second step six times, and thereversed fourth step.

The hollow cylindrical body Z fabricated by performing theabove-described steps is illustrated in FIG. 8 in the form of adevelopment view. FIGS. 9 to 11 are a front view and detailed views ofthe fabricated hollow cylindrical body Z, respectively.

As shown in the drawings, the first wire 10 of super elastic shapememory alloy constituting the first cylindrical stent member X is bent alarge number of times while being extended upwardly and downwardly alarge number of times, so the first wire 10 forms a plurality ofvariable rhombic spaces 20 by forming a plurality of intersections 70for causing the first wire 10 to be intersected with itself to resistthe longitudinal constriction of the first cylindrical stent member Xand a plurality of interlocked points 60 for causing the first wire 10to be interlocked with itself at spaced positions to allow thelongitudinal constriction of the first cylindrical stent member X.

The second wire 11 constituting the second cylindrical stent member Y isdiagonally extended in parallel with the previously positioned firstwire 10 and passed alternately under and over the first wire 10 so as todivide each of a plurality of rhombic spaces formed by the firstcylindrical stent member X into four equal parts. Hence, the first andsecond cylindrical stent members X and Y are prevented from beingseparated from each other.

After the above-described fabrication steps, the first and second wires10 and 11 are each welded together at both ends 10 a and 10 b, or 11 aand 11 b, and connected at both ends 10 a and 10 b, or 11 a and 11 b toeach other by inserting the ends into the sleeve 200 and pressing them.

The self-expandable stent 80 is completed by cutting the remainingportion of both ends of each of the first and second wires 10 and 11,removing the projected pins 120 from the base jig 100, separating thehollow cylindrical body Z of the present invention from the base jig 100and having the hollow cylindrical body Z memorize its original shapethrough a heat treatment process.

In the present invention, the heat treatment process is completed insuch a way that after the fabrication of the hollow cylindrical body Z,the hollow cylindrical body Z is allowed to memorize its original shapeat the temperatures at which the hollow cylindrical body Z does not loseits elasticity.

The heat treatment, as disclosed in the previously filed patentapplication of the present inventor, is preferably performed at atemperature ranging from 350 to 600° C. for 8 to 30 minutes.

The super-elastic shape memory alloy wire is employed in the presentinvention. In the case of a super-elastic shape memory alloy wire havinga diameter smaller than 0.1 mm, the self-elasticity of the super-elasticshape memory alloy wire is very low, so a stenosal portion cannot besufficiently expanded by the fabricated self-expandable stent and thesuper-elastic shape memory alloy wire is not reliable; while in the caseof a super-elastic shape memory alloy wire having a diameter greaterthan 0.5 mm, the hollow cylindrical body Z does not have sufficientrhombic spaces 20, so the hollow cylindrical body Z cannot besufficiently reduced in volume. Hence, the super-elastic shape memoryalloy has preferably a diameter of 0.1 to 0.5 mm.

Additionally, the number of the bends formed on each of both ends of thehollow cylindrical body Z is preferably less than 12. The reason forthis is that a large number of the bends reduce the areas of rhombicspaces 20 regardless of the diameter of the super-elastic shape memoryalloy wire, so the hollow cylindrical body Z cannot be sufficientlyreduced in volume when in use.

However, when the number of the bends is less than three, the hollowcylindrical body Z can be sufficiently reduced, but the self-expandablestent 80 has a low elasticity even though the self-expandable stent 80is restored to its memorized original shape. Consequently, the number ofthe bends is preferably three or more.

In the present invention, the first cylindrical stent member X iscomprised of a plurality of rhombic spaces 20. As a result, when thefirst cylindrical stent member X is bent by external force, the rhombicspaces 20 situated on the inside of the first cylindrical stent member Xbent are constricted whereas the rhombic spaces 20 situated on theoutside of the first cylindrical stent member X bent are expanded.Therefore, when the first cylindrical stent member X is bent by externalforce, the first cylindrical stent member X can keep its bent shape(refer to FIGS. 12 and 13).

The first cylindrical stent member X is comprised of a plurality ofrhombic spaces 20, so the rhombic spaces 20 are longitudinallycompressed when longitudinal compression force is given to the firstcylindrical stent member X, thereby causing the shortcoming that theentire length of the first cylindrical stent member X is shortened.

The shortcoming can be prevented by the second cylindrical stent memberY.

In more detail, the second cylindrical stent member Y undergoes thefabrication procedure that the second wire 11 are bent at its turningpoints while diagonally traversing the length L of the first cylindricalstent member X from one end to the other end. As a result, the firstcylindrical stent member X interlocked with the second cylindrical stentmember Y can maintain its original entire length L.

Therefore, the present invention overcomes the shortcoming of theinvention simultaneously filed in Korea in which the self-expandablestent is longitudinally constricted.

As set forth beforehand, in this embodiment, the present invention isdescribed using the circumference dividing lines a0, a1, a2, a3, - - - ,a9 and the length dividing lines b0, b1, b2, b3, - - - , b7 set byregularly dividing the circumference w and length L of the of thecylinder 110 of the base jig 100, which is for easy understanding of thepresent invention. Accordingly, the circumference dividing lines and thelength dividing lines can be optionally set according to the size of thestent 80, that is, the diameter and length of the stent 80.

A plurality of assembly grooves 130 are formed with reference to thecircumference dividing lines a0, a1, a2, a3, - - - , a9, and the lengthdividing lines b0, b1, b2, b3, - - - , b7 can be set as describedbeforehand. The base jig 100 can be fabricated using the assemblygrooves 130 and the setting.

Accordingly, expandable stents that are each fabricated of two wires andcan be deformed to have a straight line or winding shape pertains to thescope of the present invention.

The expandable stent of the present invention is utilized in the sameway as that for the method of the patent application previously filed bythe present inventors.

However, in the self-expandable stent 80 of the present invention, therhombic spaces 20 defined by the interlocked points 60 and intersections70 of the first cylindrical stent member X can be varied by externalforce. Accordingly, the self-expandable stent 80 can be deformed in itsbend such as a blood vessel or the gall duct and varied in diameter Ø,so the self-expandable stent 80 can expand the stenosal portions withinthe gullet, the gall duct or the urethra while maintaining the originalshape of the stenosal portion.

In particular, the interlocked points 60 are comprised of the spacedbends of the wires 10 and 11, so the self-expandable stent 80 does notdamage the inner wall of the blood vessel B when inserted and removed.

As described above, the present invention provides a self-expandablestent used to be situated in and expand the passage of a stenosalportion, which is capable of being positioned to fit the shape of thepassage of the stenosal portion regardless of the shape of the passage,such as a straight (horizontal or vertical) passage and a windingpassage, while maintaining its transversal elasticity, thereby expandingthe passage of the stenosal portion to its original shape.

Although the preferred embodiments of the present invention have beendisclosed for illustrative purposes, those skilled in the art willappreciate that various modifications, additions and substitutions arepossible, without departing from the scope and spirit of the inventionas disclosed in the accompanying claims.

1-3. (canceled)
 4. An apparatus for fabricating self-expandable stentusing shape memory allow, comprising: a cylinder having the samediameter and length as those of a self-expandable stent to befabricated; a plurality of assembly grooves formed along circumferencedividing lines and a length of said cylinder, said circumferencedividing lines being set by regularly dividing a circumference of saidcylinder; a fixed projected pin implanted on an uppermost portion ofsaid cylinder.
 5. The apparatus according to claim 4, further comprisinga plurality of assembly auxiliary grooves, said assembly auxiliarygrooves being each formed between two neighboring assembly grooves.